I'm using Blender to do some 2D, shape-based animation.

Everything you see here is a Bézier shape. To animate the mouth and eyes independently, I add holes to the head shape and then stack the eye and mouth parts below it with an orthogonal camera.

This works OK, but it's not perfect. For one, I have to make sure that none of the inner shapes peek out from behind the head shape. I also have micromanage the hole shapes whenever I change the outer head shape, e.g. to prevent edge contact and self-intersections. Instead of making holes, I wish I could simply add a mouth-shaped mask to the mouth group and then animate the mask independently, but it seems impossible to do this. I know that I could convert the paths to meshes using Alt+C and then add a boolean modifier, but this would no longer allow me to modify the control points. I've also seen approaches that use the compositor to create masks, or that use render layers to create portals, but they all seem far too heavyweight for use as simple masks.

Is there any way I could apply a Bézier mask to a group of shapes in Blender?